The hearing, or auditory system is well understood. When a noise occurs, it sends vibrations through the air much like ripples on a pond. These enter the ear canal or outer ear, and make their way to the ear drum. The human eardrum is a stretched membrane, like the surface of a drum. When the sound waves hit your eardrum a chain reaction is set off. Three of the smallest bones in your body, the hammer, anvil and stirrup help to amplify the sound and transmit it to the inner ear or cochlea. The inside of the cochlea is lined with thousands of hair-like nerve endings called cilia. When the sound vibrates the cochlea, the cilia move. This movement sets off another reaction which allows the message to reach the brain via the auditory nerve. The brain in turn interprets the sound and gives it meaning. Neurologists don't yet fully understand how we process raw sound once it enters the temporal lobes of the brain.
Just above the cochlea lies a closely related system called the vestibular system. This system is responsible for balance and the sensation of movement. These tiny loops or semi circular canals are filled with fluid that moves when you move your head. Like the cochlea, tiny cilia line the inside, and when your head moves, the fluid moves in turn stimulating the cilia. This stimulation sends a message to your brain telling you how your body is moving. Interestingly the fluid in the cochlea runs continuous with part of the fluid in the semi circular canals. In certain disorder such as Meniere’s disease, both the vestibular and auditory systems are affected and a person might experience hearing loss accompanied by balance problems.